International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. B. ch. 3.3, p. 373
Section 3.3.1.3.11. Other useful rotations
aMRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, England |
If rotations in display space are to be controlled by trackerball or tablet then there are two measures available, an x and a y, which can define an axis of rotation in the plane of the screen and an angle θ. If x and y are suitably scaled coordinates of a pen on a tablet then the rotation with is about an axis in the xy plane (i.e. the screen face) normal to and with . Applied repetitively this gives a quadratic velocity characteristic. Similarly, if an atom at in display space is to be brought onto the z axis by a rotation with its axis in the xy plane the necessary matrix, in homogeneous form, is with .